1. Field of the Invention
The present invention relates to a clock signal generating system to reproduce data from a recording medium and a data reproducing apparatus, and more particularly, to a clock signal generating system generating a control clock by selectively using an RF signal and a wobble signal from a recording medium, and a data reproducing apparatus using the clock signal generating system.
2. Description of the Related Art
Generally, when data on a recording medium such as a DVD, a CD, and a DVD-ROM is reproduced, a clock signal is generated from an RF signal on the recording medium through a phase synchronization loop circuit.
In a recordable medium, such as a CD-R, a CD-RW, and a DVD-RAM, concentric tracks from a center of a disc are formed on a surface of the disc. In order to record data at a desired location of the disc surface, a procedure that traces a track having a desired location and then records the data at the desired location is needed. To implement this procedure, a series of jobs are needed to identify location information where a pickup of the optical disc is to be placed. To enable these jobs, a wobble signal having a predetermined frequency is formed on the surface of the disc.
According to the related art, a header in which location information of the disc is recorded based on a predetermined rule is inserted in a middle of the wobble signal, and by reading the header, a current location or an address is determined.
FIG. 1 is a diagram of a part of a DVD-RAM disc structure where the wobble signal and the header information signal are recorded along the track.
A method, in current systems, in which the current location is determined by reading a header signal formed by a predetermined rule leads to complicated disc manufacturing processes. Also, because the wobble signal is not clearly reproduced in a sector where the header is placed, a generation of a phase-locked loop (PLL) signal using the wobble signal needs a special compensation circuit.